River Ash Tree
Riverdave's Journal
This essay appeared in the Durham Herald-Sun on 11/1/1998

The river ash is a very common tree along the banks of the Eno River. It often leans at a 45 degree angle over the water, along with its companion species the river birch, river elm and river maple. Together they create for the paddler a delightful tunnel of green through which to pass. The ash tree occupies this midlevel, canopy position above the ironwoods and below the sycamores in a Piedmont riparian forest. Often the trunk is covered with a green moss which I don't find as commonly on its companion trees mentioned above. The compound leaves of the river ash are an exceptionally shiny green and stand out erectly and distinctly against the background foliage of its neighboring trees. I have found it often to be a host tree to a  semi-parasitic mistletoe, this phenomenon being more easily observed in the winter when the river ash is bare of its leaves.

Ash trees provide the wood for athletic equipment because of their toughness, straight grain and most of all, its elasticity and resilience. The first choice for makers of bats, mallets, racquets and paddles was a sister species, the white ash, Fraxinus americana, an upland  tree. But as white ash has become scarcer, river ash, Fraxinus pennsylvanica, has begun to replace it in manufacturing even though it is a slightly heavier wood. At the lower, eastern end of the Eno River, one may also begin to encounter still another species of ash, the Carolina ash, Fraxinus caroliniana, a tree that extends still further south, even into the West Indies.

The small, greenish flowers of the river ash are very inconspicuous, but it is through its distinguished fruit that we learn of the trees fine wafting capabilities. The fruit is a winged seed, or key, as it is often called, about an inch and a half long and one quarter of an inch wide. The actual seed is fastened to the narrow end of this flattened structure, leaving the wider end of the key to act as a rotor blade. Clusters of dozens of these fruits mature together at the end of a twig and by autumn are ready for dispersal. The jolting pounce of a squirrel on a limb that is laden with ripe fruit or a sudden, big gust of wind will jar loose hundreds of these seeds and send them wafting through the air, twirling about like tiny helicopters onto the water or nearby river bank. It is quite a mesmerizing and entertaining sight to observe.

The river ash could have evolved to simply drop its seeds straight down, not having wings like an acorn. But the waft is in the wings and with them the seed is able to travel a much farther distance, being buoyed up in the wind and kept aloft for a greater period of time. And since its seed is heavier than that of the champion wafter, the light and puffy willow seed, it requires more locomotion than the willow's delicate parachute of fiber to keep it aloft. A differing aerodynamic wingmanship is employed by the ash tree, similar to that which is found in many other trees such as our local pines and maples.

I have always stood in admiration of the helicopter seed. In March of this year I visited for the first time the island of Abaco in the Bahamas during its winter dry season. While exploring its West Indian subtropical forest, I noticed a very large, capsule-like fruit standing erectly on what seemed to be a fairly common tree. I reached up and picked one that was beginning to cleave open. As I plucked it off, the hull split completely apart into five sections and out fell dozens of beautiful, tan, winged seeds, looking similar in design to those of the river ash.

A quick search in my field guide revealed that it was the fruit of the well known West Indian mahogany tree. I tossed the remains of the capsule into the air and once again admired and saluted this squadron of dandy helicopters that wafted away through the air. While reporting my find to a resident of the nearby fishing village of Cherokee, I was happy to learn that the chief use of mahogany by the local population was for ribs in boat building. So the waft continues on ...

In our Triangle area, only one tree might be visually confused with the river ash and that is the river maple, or box elder as it is sometimes called. Several characteristics make the keys of the river ash readily distinguishable from those of its sister tree, the river maple, which possesses a similarly shaped fruit. First, the keys of the ash tree seem to be more numerous in sheer volume than those of the maple. Secondly, the keys of the ash tree are released in clusters in late autumn while the maple keys usually persist on the twig into winter, falling one by one. Finally, the seeds of the river ash are attached as single keys while the maple keys dangle as attached pairs of twins.

While paddling the Eno River in the autumn season, if I come across a branch of ash bending low over the river that hasn't yet been disturbed by the elements, I find myself eager to create a wafting spectacle. I'll then reach up from my boat, grab the limb and give it a good shaking, entertaining myself with the visual delight of hundreds of whirling dervishes spinning off and wafting through the air.
Photo by Paul Wray, Iowa State University, green ash seeds